Leyton Orient boss Richie Wellens said:
"The players put an unbelievable effort in. We had players back from illness and it's an amazing night for the football club with a youth product scoring the winning penalty.
"I thought for the first 60 minutes we were the better team but we needed to pass the ball better at times.
"Derby are a good team and they have lightning wingers and I thought they could score on the counter-attack but the stadium felt alive tonight especially at the end.
"The magic of the FA Cup is alive and perhaps we can beat Man City in normal time. I'm delighted for the chairman."
Derby County boss Paul Warne speaking to BBC Radio Derby:
"I don't think we did enough to win the game. I don't think we were aggressive enough in the challenge.
"I thought we had moments of good play. We looked a little bit soft in the middle of the park in the first half. We didn't create enough, we didn't make the goalkeeper make enough saves.
"It was a pretty stalemate kind of night. I don't think they were any better than us and nor should they be."
On potential new players: "It might need new faces, it might need freshening up.
"I thought a few of the lads didn't perform as well tonight and we have to try and pick a team away from home that's going to be resolute but also create chances.
"They game had enough tonight to win, we made positive chances, but unfortunately tonight we didn't.
"We need something in the middle of the park, we need something out wide, we need more goal threat and that's what everyone's trying to do."